Gambler sues, claims he was blackout-drunk when he lost $500,000

However, a California businessman claims he never should have been allowed to go $500,000 into debt at the Downtown Grand Las Vegas, and he's filed suit.

An attorney for Mark Johnston claims Nevada gaming regulations prohibit casinos from letting those visibly drunk from gambling. Johnston is trying to get his debt erased.

Johnston said he was invited to stay at the Downtown Grand over Super Bowl weekend by a casino host he knows. The civil complaint indicates he drank before and after his flight to Las Vegas, later having dinner and more drinks at the Triple George Grill downtown.

"He has no recollection of leaving Triple George or the next events of the next day and a half," said Johnston's attorney, Sean Lyttle.

The complaint refers to this as the "blackout period." Johnston claims he can't remember events that transpired over a 44-hour period.

The complaint cites witnesses who said he showed obvious signs of intoxication, but that the casino kept serving him drinks and letting him play blackjack and pai gow.

The suit claims that over 11 hours, the casino allowed him to take out four lines of credit totaling $500,000.

"Playing on credit is out of the ordinary. Drinking to the point of intoxication is out of the ordinary, as the Downtown Grand should have known," Lyttle said.

The complaint claims that when Johnston sobered up, the casino told him that he received a 20 percent discount and owed $400,000 by the end of March.

"After they got the letter, they took the markers and jammed them through my bank. They sneakily sent the whole $500,000 through when I didn't even owe that, tried to steal $100,00 from me, and the money is not even due until March 31," Johnston said.

Johnston said he's been a high roller in Las Vegas casinos for decades. He's asking for a jury trial.

FOX5 contacted the Downtown Grand for comment on this story, but were told this is an ongoing lawsuit and it's policy to not speak publicly about pending litigation.